The aviation authority requires that gas turbine engine casings must be capable of containing the release of a single or multiple compressor or turbine blade(s). The “fan-blade-off” test is a single-shot test where a projectile is released explosively and the mechanical integrity of all systems and the containment capability of the engine casing is assessed following the projectile release.
The projectile is typically a fan blade (full sized or scaled) or a fan blade fragment.
The test may be an engine test or a rig test which are expensive and require long lead times. Often a reduced cost but complex ballistic test is used to simulate the fan-blade-off-test.
These known ballistic test methods fail to take account of the nature of blade impact in terms of impact angle and loading. In real-life fan-blade-off incidents, the blade impact comprises a highly oblique initial impact of the blade body followed by a second highly oblique impact of the root portion of the blade. Ballistic tests often fail to replicate these impact angles and feature projectiles which permanently deform unrepresentatively due to differences between a rotating and linearly translating projectile.
The present invention aims to provide an improved projectile for use in simulated fan-blade-off tests, where the projectile accurately simulates the nature of a blade impact.